When was the last time we spent so much mental energy attempting to decipher the result of a TopSpiel? The weekly Saturday early evening showcase in the Bundesliga is often the biggest and best of the weekend and a game that intrigues and satisfies, but this latest episode of Borussia Dortmund versus RB Leipzig caught us all on the hop.

The wind, after all, seemed to be blowing one way. BVB had suffered three consecutive defeats with varying degrees of misery – the eventual 5-2 loss at Real Madrid in which they had played pretty well for most of the game, the 2-1 at Augsburg in which they certainly didn’t, and the extra-time 1-0 loss at Wolfsburg in midweek which ended their interest in the DfB Pokal. There was little to suggest that Dortmund were the team to bring Leipzig’s 19-game unbeaten run in the Bundesliga to a juddering halt. Yet Nuri Sahin’s side did just that and convincingly so, with style and substance. It was a result that required a thorough explanation.

Both coaches offered their own theories. Sahin put forward a blast from the past, revealing he went back over the copious notes he took as a player with coaching aspirations and tried an old Thomas Tuchel tactic which had helped his team roll over Leipzig in the incendiary first version of this fixture back in 2017. Tuchel had used a single defensive midfielder, a ball-playing midfielder in a deeper role, to exploit the spaces left in Leipzig’s 4-2-2-2. The plan had been to use Sahin himself but, as regrettably often during his second spell at the club, he was injured so Julian Weigl filled the role instead. Felix Nmecha stepped in on Saturday and “the boy did very well,” in Sahin’s words.

On the other side, Marco Rose suggested his team, one of the Bundesliga’s very best, showed a lack of experience in dealing with the occasion. “In games like this, where we [have the chance to] pull away and get ourselves a statement win,” Rose lamented, “we can lack courage and conviction. We need to take it as a lesson for the next few weeks. As a Champions League team, we have to believe in ourselves more in stadiums like this, against opponents like this.”

These games are rarely damp squibs. It is not a derby or a Klassiker, but when Borussia Dortmund and RB Leipzig meet it is more than a match and more than a bit of needle. It is a clash of diametrically opposed philosophies, recently brought more sharply into focus by Jürgen Klopp’s surprise move to Red Bull, which profoundly shook many Dortmunders. If the array of anti-RB banners on the Yellow Wall will never match the sea of them that came out to float on Leipzig’s first visit in 2017, some still appeared on Saturday, a few taking issue with Klopp himself.

What gives this game its extra edge is BVB’s self-appointed role – seen as self-righteous by many rival fans – as a protector of German football’s traditional values. Yet all these years on from Leipzig’s introduction to the top flight, some observers have started to broach the question of whether those traditions are limiting, Klopp’s choice hinting that might be a growing feeling among people in the game. “When Klopp starts on 1 January,” wrote Bild’s Alfred Draxler in a recent editorial, “he can do whatever he wants with leaner structures and less sentimentality.”

In terms of the current picture, there appears to be a growing gap in terms of focus and strategy. Already, this match felt potentially season-defining. A win at Signal Iduna Park would have moved Leipzig 10 points clear of BVB. Now the gap is just four, which seems a modest expression of what has felt like a real gulf between the two teams’ directions in the opening stanza of this season. That is a relief to Dortmund, and to Sahin. Any pressure on the rookie coach has been from the outside rather than inside the club – there is an acute awareness a rebuild will take time – but that has not diminished the discomfort or alarm in the team’s chaotic season so far.

All of which made this performance – one of passion, invention and composure – such an exhilarating surprise for those of a black-and-yellow persuasion. The hosts had started well but when Benjamin Sesko gave the visitors the lead with their first effort on target – and Jamie Gittens missed an almost immediate chance to equalise – there was no panic. Maximilian Beier levelled with his overdue first goal for the club before later eking out the cross from which Serhou Guirassy headed home the winner.

It should not have been possible. Injuries have left Sahin over a barrel. Leipzig’s Willi Orban regretted his side’s inability to raise the tempo “because we knew that Dortmund might have problems bringing quality off the bench”. When naming his squad for the match on Friday, Sahin had called up eight players from the under-23s to supplement his first team. One of them, Ayman Azhil, made his debut as a substitute in the second half when Marcel Sabitzer was unable to carry on.

Beier’s form thus far had hardly demanded inclusion, but the current personnel situation had demanded he persevere, and that Sahin persevere with him. Now, this could be a landmark game for the young forward, signed for €30m from Hoffenheim this summer. Whether it will be for BVB, only time will tell. There are likely to be further setbacks. But the relief that under such pressure and an avalanche of absences there is still a way to be found is relief enough for now; and perhaps as importantly, an endorsement of their continued identity.

Talking points

• The big winners of the weekend were Bayern, with Harry Kane’svirtuoso centre-forward display –with two goals and a delicious assist for Kingsley Coman – steering them to a comfortable 3-0 win over a gnarly Union Berlin, moving them three points clear of Leipzig at the summit. Seeing Bayern begin to recover their merciless selves reminds us how long they have been below club standards; a third consecutive Bundesliga clean sheet was, remarkably, their first in four-and-a-half years. Now, attention turns to the Champions League, where two defeats in three have made Wednesday’s visit of Benfica a big one or, as João Palhinha said: “A final for us.”

• Perhaps even more pertinently, Bayern now lead Leverkusen by seven points after the champions dropped points for a second straight week in a home stalemate with Stuttgart. Matches between last season’s top two have been unmissable for a while so a goalless draw was a genuine shock. The main architect of the result was visiting goalkeeper Alexander Nübel, outstanding in keeping Leverkusen at bay as he pitches to be Germany’s No 1. There was strange satisfaction for Die Werkself at a first Bundesliga clean sheet and what Granit Xhaka described as “definitely our best performance of the season”, before Xabi Alonso’s Tuesday return to Anfield.

• Three cheers too for Holstein Kiel, first-time winners over Heidenheim and now four points clear of last place after crisis club Bochum were flamed 7-2 at Eintracht Frankfurt, who sit third.